1. Technical Field
This invention generally relates to fuel sensors. More particularly, this invention relates to a fuel sensor arrangement having a single capacitor that is used in two different modes to determine desired characteristics of a fluid such as a fuel mixture.
2. Description of the Prior Art
A variety of fuel sensors are known. Fuel sensors typically are used to determine the content of a fuel mixture within a fuel system of a vehicle. Some sensors are capable of determining the content of the fuel mixture such as a ratio or proportion of alcohol to gasoline within the fuel. Depending on the determined ratio, the ignition timing and fuel quantity supplied by fuel injectors may be adjusted by a suitable fuel flow control system.
It is known that the relative permittivity of gasoline differs from that of alcohol because of the different oxygen levels within each. Alcohol and gasoline also have different conductivity. Accordingly, the relative alcohol content of a fuel mixture is a well-defined function of the fluid's relative permittivity, temperature and conductivity.
Known sensors take advantage of these known characteristics of fuel mixtures and utilize the electrical properties of the fuel contents to make a determination regarding alcohol level within a fuel, for example. Sample patents in this field of endeavor include U.S. Pat. Nos. 4,945,863 and 5,367,264. Each of these patents show approaches to providing a fuel sensor that utilizes the electrical properties of the fluid for making fuel content determinations.
While the current approaches have proven satisfactory, those skilled in the art are always striving to make improvements. For example, packaging constraints on vehicle systems continuously cause an emphasis to be placed upon minimizing the size of components and maximizing the convenience of integrating them into vehicle systems. Additionally, cost savings are always a concern to automotive suppliers.
This invention addresses the need for providing a more economical and more convenient approach to fuel sensing technology.